(1) Field of the Invention
The present invention relates to a method for building or repairing rotary fuel injection pump timing piston cylinders. In particular the present invention relates to a unique sleeving method.
(2) Prior Art
Regulating the timing of fuel injection in rotary pumps has been directed to changing the position of a timing control piston under various engine operating conditions. U.S. Pat. No. 4,224,916 to Charles W. Davis discloses a timing control for a rotary fuel injection pump wherein the position of a timing piston is adjusted in response to the increase in engine speed. U.S. Pat. No. 4,432,327 describes an improved timing control for a fuel injection pump using a drainage passage and valve for outlet from a cylinder housing a timing piston. U.S. Pat. No. 4,453,522 to Daniel E. Salzgeber discloses a means for effecting the position of a timing piston and consequently the advance of the fuel injection to compensate for conditions when the engine is cold.
U.S. Pat. No. 4,432,327 describes the operation of rotary fuel injection pumps in a particularly effective manner and this disclosure is incorporated herein. Obtaining precise timing of the fuel injection into an engine cylinder in relation to the top dead center (TDC) position of the piston is a critical factor in minimizing the discharge into the environment of pollutants from the exhaust of the internal combustion engine, as well as minimizing the engine noise level. More precise regulation of the timing of the fuel injection is necessitated by increasing environmental considerations and regulatory mandates. Improved injection timing regulation results from both a more precise means for advancing and retarding the timing of fuel injection and also sensing means for taking into account more operating parameters of the engine when determining the optimum degree of timing advancement of retarding to be applied.
The injection of fuel in compression-ignition or diesel engines normally occurs at a time when the piston is in the vicinity of its TDC. The desired time of fuel injection varies for different engine designs and ranges from a time slightly prior to TDC to a time slightly after TDC. In the normal course of operating an engine, various operating parameters such as speed, load, engine temperature, and altitude may vary over ranges which require timing adjustments which are substantial enough to have a significant impact on obtaining optimum timing of fuel injection.
A number of general considerations have been established. As the engine speed in r.p.m. increases, the timing of fuel injection should normally occur earlier relative to TDC. The time interval for fuel to flow from injection pump to injection nozzle is not a function of engine speed although the time required for combustion in the engine is a function of engine speed. Therefore, a mechanism is frequently employed to adjust the timing of fuel injection to compensate for wide ranges in engine speed. A second important factor requiring timing adjustment may result from engine load differences or changes in r.p.m. For example, advancing the timing of fuel injection for fast acceleration is generally advantageous. A third timing adjustment may be required to compensate for engine temperature. It is generally advantageous to advance the timing of fuel injection in a cold engine operating at relatively low speed. A fourth factor for which an adjustment in injection timing is desirable is the altitude at which the engine is operating. In general, at higher altitudes the timing of fuel injection should be advanced. Other factors, such as pump wear and fuel density, may also require an adjustment of the setting of the timing mechanism to obtain the desired timing of injection.
In rotary fuel injection pumps, wherein position changes of a cam contour or lobe around the axis of rotation is translated into pumping strokes of plungers around a rotor actuated by the cam lobes, the fuel injection timing is provided by a timing control acting on the cam to advance or retard the timing of the injection pumping stroke, and to consequently provide for a control of the timing of the injection of fuel into the engine cylinder. A timing control piston is provided which mechanically interacts with the cam to advance or retard the timing corresponding to the relative position of the piston in a hydraulically (fuel) controlled cylinder. This control piston is thus very active in the operation of the engine and rapidly causes wear of the cylinder in which it is housed.
The rapid wear of the timing piston cylinder is because of two factors: (1) inexpensive epoxy impregnated aluminum housing castings; and (2) pistons which are made of materials which are much harder than the wall of the cylinder. This problem causes leakage around the control piston thus interfering with proper operation. Further, an expensive fuel pump can fail in as little as a few hundred to a few thousand miles of vehicle use depending upon the composition of the wall of the cylinder. This problem has caused large losses in warranty repairs and has defied a reliable and inexpensive solution.
Various methods have been tried to build or repair the wall of the cylinder for the control piston. This includes brass sleeves to refurbish the cylinder, cylinder wall and/or plating of the wall with nickel. These repairs have met with limited success and are not durable.